1. Field of the Invention
This invention relates to an orthodontic wire supporting device such as a bracket adapted to guide a piece of wire placed across selected teeth during an orthodontic treatment.
2. Description of the Related Art
Abnormal occlusion, for example, due to mal-aligned dentition has usually been corrected by so-called orthodontics intending to obtain a normal occlusion by moving mal-aligned teeth to their aligned positions. The orthodontic treatment is carried out by placing a piece of orthodontic wire 1 across selected teeth, as shown by FIG. 9, and then by moving the mal-aligned teeth toward their normally aligned positions under a lateral pressure exerted by the piece of wire 1.
FIG. 9 illustrates a manner of orthodontic treatment. As seen in FIG. 9, wire fixing devices 3 are mounted on first molars 2a, 2b of right and left sides, respectively, and opposite ends of the piece of wire 1 are fixed to the wire fixing devices 3, respectively, so that the piece of wire 1 extends between the first molars 2a, 2b along front sides of premolar and anterior teeth. Sometimes the wire fixing devices are mounted also on second molars 4a, 4b of right and left sides, if necessary to hold the opposite ends of the piece of wire 1 more reliably.
A bracket 6 serving as a wire supporting device adapted to guide the piece of wire 1 is attached to front sides of the teeth to be corrected and the piece of wire 1 is guided by this bracket 6 between the first molars 2a, 2b. The respective teeth necessarily shift more or less as the orthodontic treatment progresses. Accordingly, it is essential to hold the piece of wire 1 slidably relative to the bracket 6 without any apprehension that the piece of wire 1 might unintentionally fall off from the bracket 6. The opposite ends of the piece of wire 1 define reference positions for the orthodontic treatment. Accordingly, it is important that the opposite ends are fixed on the respective wire fixing devices with a sufficient stability to prevent the piece of wire 1 from slipping out of place relative to the first molars 2a, 2b. Simultaneously, it is also important that the wire fixing devices 3 are fixed on the first molars 2a, 2b with a sufficient stability to prevent the devices 3 from unintentionally falling off.
While the wire fixing devices 3 are firmly bonded to the first molars 2a, 2b (sometimes also to the second molars), the bracket 6 must be attached to each tooth so that the bracket 6 can be easily detached from the tooth when it is desired. More specifically to describe, the tooth necessarily shifts as the treatment progresses and, at the position thus shifted, the piece of wire 1 cannot be properly guided by the bracket 6. In this case, the bracket 6 must be detached from the tooth in order to be exchanged with a fresh one. The bracket 6 must be detached also upon completion of the treatment. So long as the piece of wire 1 is being guided by the bracket 6, it would be inconvenient for the treatment that the bracket 6 might fall off from the tooth. Accordingly, the bracket 6 must be properly bonded to the tooth.
FIG. 8 is a perspective view schematically showing a configuration of the conventional bracket 6. This bracket 6 comprises a substantially rectangular base 61 destined to be bonded to the teeth, a bridge-like portion 62 integrally rising from the base 61 in the middle thereof and a guide groove 63 formed in a top of the bridge-like portion 62 in the middle thereof so as to receive the piece of wire 1.
As has been described above, it is required for the bracket 6 to be reliably held on the front side of the tooth so long as the piece of wire 1 is being guided by the bracket 6. It is also required for the bracket 6 to be easily detached from the tooth in view of the fact that the bracket 6 must be often exchanged with a fresh one as the treatment progresses. However, with the above-mentioned bracket 6 of the prior art, it depends on an adhesive effect of used adhesive agent whether the bracket 6 can be easily detached from the tooth or not, since the bracket 6 is usually bonded to the tooth by means of adhesive coating the base 61 of this bracket 6. Use of an adhesive agent presenting a relatively high adhesive effect certainly assures that the bracket 6 is firmly held on the tooth during the orthodontic treatment. However, use of such adhesive agent will make it difficult to detach the bracket 6 from the tooth, for example, when it is desired to exchange the bracket with a fresh one and correspondingly will make the operation of exchange troublesome. Use of an adhesive agent tending to facilitate the operation of exchange may cause the bracket 6 to fall off during the treatment and make the desired treatment impossible. Additionally, it is required for a dentist to select the most suitable adhesive agent from various types of adhesive agents depending on the particular material of the bracket 6 and this is a burden which is not negligible for the dentist.